EE1002_CG1108_Tutorial_questions - EE1002/CG1008 Tutorial 1...

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Unformatted text preview: EE1002/CG1008 Tutorial 1 1. Use Kirchoff’s current law to determine the unknown currents in the circuit of the Figure 1Error! Reference source not found.. Assume that I0=‐2A, I1=‐4A, Is=8A and Vs=12V. R4 a I2 I1 I0 R0 R1 R2 b IS VS I3 R3 Figure 1 Ans. I 2 6 A, I 3 2 A 2. Apply KVL to find the voltages v1 and v 2 in the Figure 2. 3V 10V v2 v1 Figure 2 Ans. v1 12V , v2 2V 1 of 11 3. For the circuit given in Figure 3, a. Determine which components are absorbing power and which are delivering power. b. Is conservation of power satisfied? Explain your answer. 3V 2A B A D 5V 3A C E 10V Figure 3 Ans: Absorbing power: C,D,E; Delivering power: A,B 4. In the circuit given in Figure 4, the power absorbed by the 15‐Ohm resistor is 15W. Find R. R 4 6 15 4 24 4 Figure 4 Ans. R 4 2 of 11 EE1002/CG1108 Tutorial 2 5. For the circuit shown in Figure 5, find: a. The currents i1 and i2 . Ans. i1 1.8 A, i2 1.2 A b. The power delivered by the 3A current source and by the 12V voltage source. Ans. 279W ,6.17W c. The total power dissipated by the circuit. Ans. 285.17W R1=25 ohm, R2= 10 ohm, R3=5 ohm, R4=7 ohm . R1 R3 i2 i1 R2 R4 Figure 5 6. Given the circuit of Figure 6: a) Determine the power delivered by the dependent current source. Ans. 108W b) Determine the power delivered by the voltage source. Ans. 0W 15 7 i 0.5i 2 5 Figure 6 3 of 11 7. Consider NiMH hobbyist batteries shown in the circuit of Figure 7: a. If V1=12.0V, R1=0.15 ohm, RL=2.55 ohm, find the load current IL and the power dissipated by the load. Ans. I L 4.44 A, PL 50.4W b. If we connect a second battery in parallel with battery 1 that has voltage V2=12V and R2=0.28 ohm, will the load current IL increase or decrease? By how much? Use mesh current analysis method. Ans. Increases by 0.09A IL R1 RL V1 Battery 1 Load I1 I2 IL R2 R1 RL V2 V1 Battery 2 Battery 1 Figure 7 4 of 11 Load 8. Using node voltage analysis in the circuit of Figure 8, find the current i through the voltage source. Ans. i=8.03A 0.5 i 0.5 0.25 0.33 Figure 8 9. Using KCL, perform node analysis in the circuit shown in Figure 9 and determine voltage across R4. Note that one source is a controlled voltage source Vs=5V, Av=70, R1=2.2kohm, 2=1.8kohm, R3=6.8kohm, R4=220ohm. Ans. 8.757mV vR1 R1 R2 R3 Vs AV VR1 R4 Figure 9 5 of 11 EE1002/CG1108 Tutorial 3 10. Determine, using superposition, the voltage v across R in the circuit of Figure 10. I B 3 A, RB 1,VG 15V , RG 1, R 2 Ans. v=7.2V RG IB RB R VG v Figure 10 11. Find the Thevenin equivalent circuit that the load ( R L ) sees for the circuit of Figure 11. Ans. Vth=4.499V, Rth=504 ohm 1k 10V 1 1k 3 1mA RL Figure 11 6 of 11 12. For the circuit given in Figure 12: (i) Obtain the Thevenin’s equivalent for the circuit which contains a dependent voltage source. Ans. Vth=30V, Rth=10 ohm (ii) What should be the optimum value of a load resistor RL to be connected between a and b so that the power delivered to it by the network is maximum? Ans. RL=10 ohm (iii) What is the maximum power? Ans. 22.5W 4A Figure 12 7 of 11 EE1002/CG1008 Tutorial 4 13. If the switch in the circuit of Figure 13 is closed at t=0, a) Determine the current flow through the resistors and the capacitor when t=0+. Ans. i1 5 A, i2 0 A, i3 5 A b) What will be the current flow under steady state condition? Ans. i1 i2 2.5 A, i3 0 A c) Determine the voltage across the capacitor under steady state condition. Ans. 50V d) Find an expression for the capacitor voltage as a function of time t>0. Ans. 50(1 e 1 2010 6 ) Assume that the capacitor is initially uncharged. t0 20 20 2 F Figure 13 14. For the circuit shown in Figure 14, assume that switch S1 was closed and switch S2 was opened for a long time. Then, at time t=0, switch S1 is opened and switch S2 is closed. a. Find the capacitor voltage vc(t) at t=0+. Ans. 20V b. Find the time constant for t>=0. Ans. 56 S c. Find an expression for vc(t), and sketch the function. Ans. 12 8e t 5610 6 8 of 11 4 S1 5 4F 4F 30V vc S2 6 6 4A Figure 14 15. For the circuit given in Figure 15, switch S2 was closed for a long time before t=0. At t=0, the switch S1 is closed and S2 is opened. a. Find the inductor current i(t) at t=0+. Ans. 2A b. Find the time constant for t>=0. Ans. 1S c. Find an expression for i(t). t Ans. 0.667 1.333e d. Find i(t) for each of the following values, the time constant, twice the time constant, five times the time constant and ten times the time constant. Sketch the function. Ans. i ( ) 1.115 A, i (2 ) 0.847 A, i (3 ) 0.733 A, i (5 ) 0.675 110 6 20 S1 20 S2 20 i(t) L 30 H 2A 50 Figure 15 9 of 11 EE1002/CG1108 Tutorial 5 16. For the circuit in Figure 16, a) Find the expression for v R (t ) . b) If the sinusoidal has a frequency of 10 kHz, and the inductor is 1 mH , what is the value of R for phase difference between v s (t ) and v R (t ) to be 45 deg? Ans. 62.832 ohm c) Draw the phasor diagram showing the v s (t ) and v R (t ) for part (b). vL L vs (t) Vm sin( t) R vR Figure 16 17. Determine the current i(t) in the circuit shown in Figure 17. vs (t ) 636 cos 3000t 12 R1 2.3k , R2 1.1k L 190mH , C 55nF Ans. i (t ) 0.2814 cos(3000t 22.56 0 ) A i(t ) R1 R2 v s (t ) L C Figure 17 10 of 11 18. Find the Thevenin equivalent of the circuit as seen from terminals a‐b for the circuit shown in Figure 18. Ans. Vth 5 215 0 , Z th 8 j8 j 8 a j8 5 300 8 b Figure 18 11 of 11 ...
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This note was uploaded on 12/13/2011 for the course ELECTRICAL EE1002 taught by Professor Panda during the Spring '11 term at National University of Singapore.

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